1. Field of the Invention
The present invention relates to a temperature sensing circuit, voltage generation circuit, and semiconductor storage device for use in, e.g., a ferroelectric memory which includes a memory cell using a dielectric capacitor.
2. Description of the Related Art
In conventional semiconductor storage devices, a sense amplifier supply voltage to be supplied to a sense amplifier and used by the sense amplifier to compare and amplify bit line potentials and a dummy capacitor driving voltage to be supplied to a dummy capacitor and used to generate a reference potential which is supplied to one bit line when the bit line potentials are compared and amplified are generated entirely independently of each other. Accordingly, even if the sense amplifier supply voltage used by the sense amplifier to compare and amplify the bit line potentials fluctuates by a leakage current or the like, the dummy capacitor driving voltage for generating the reference voltage does not fluctuate following this fluctuation.
However, letting ΔVSA be the fluctuation in sense amplifier supply voltage VSA used by the sense amplifier to compare and amplify the bit line potentials and ΔVDC be the fluctuation in dummy capacitor driving voltage VDC, a relationship indicated byΔVDC≅α×ΔVSA  (1)holds. Therefore, it is necessary to make the dummy capacitor driving voltage follow the fluctuation in sense amplifier supply voltage on the basis of a predetermined ratio, but this has not been taken into consideration in any conventional devices.
The dependence of the dummy capacitor driving voltage VDC on the sense amplifier supply voltage VSA will be qualitatively explained below with reference to FIGS. 36A and 36B. First, assume that a residual polarization amount PrSAL as “1” data is to be read out in FIG. 36A. Letting VPL be an electric potential for driving a plate line, VBL be a bit line potential, and VSAL be a voltage to be supplied to the sense amplifier, the polarization exists in a point A when the plate line is driven, the sense amplifier is activated, and the plate line potential is returned after that.
Also, as shown in FIG. 36B, letting VSAS (VSAL>VSAS) be a voltage to be supplied to the sense amplifier, the polarization exists in a point B when the plate line is driven, the sense amplifier is activated, and the plate line potential is returned after that. That is, if the voltage to be supplied to the sense amplifier is low, the polarization moves on a small hysteresis, and the residual polarization amount PrSAS also decreases. Consequently, a “1” signal potential for the read operation, a middle point between a “0” signal potential distribution and “1” signal potential distribution, and the electric potential of the dummy capacitor driving voltage VDC also decrease.
In addition, a temperature sensing circuit as the prior art includes a circuit in which a diode and resistors Ra and Rb are connected in series, a reference potential VREF independent of the temperature, and an operational amplifier. The reference potential VREF is input to one input terminal of the operational amplifier, and a voltage VTMP at a connecting point between the resistors Ra and Rb is input to the other input terminal. The voltage VTMP is an electric potential depending on the temperature. Therefore, if the reference potential VREF changes, the reference potential VREF at which the output from the operational amplifier inverts also changes in accordance with the temperature. The temperature can be sensed by monitoring the reference potential VREF at which the output from the operational amplifier changes. Unfortunately, this method has the problem that the operating point of the operational amplifier changes.
Furthermore, in a circuit which changes a voltage to be supplied to the circuit in which the diode and resistors Ra and Rb are connected in series, and compares the output voltage VTMP of this series circuit with the reference voltage VREF by the operational amplifier, two types of electric potentials must be supplied, and two operational amplifiers are necessary to supply these electric potentials. This increases the factors of variations in threshold values.
Note that as the prior art related to the temperature sensing circuit described above, a temperature detection circuit is proposed (e.g., Jpn. Pat. Appln. KOKAI Publication No. 6-347337). This temperature detection circuit comprises a first circuit including at least one element which changes its electrical characteristics in accordance with the temperature, and so designed that the output voltage shows a temperature dependence, a second circuit including at least one element which changes its electrical characteristics in accordance with the temperature, and so designed that the output voltage shows a temperature dependence opposite to that of the output voltage of the first circuit, and a comparator which receives the output voltages of the first and second circuits.